Heat the olive oil and butter in a large skillet over medium heat.
Add the sliced onions and cook for about 10 minutes, stirring occasionally until they start to soften.
Sprinkle the sugar over the onions and continue to cook for another 15-20 minutes, stirring frequently, until the onions are deep golden brown and caramelized. Remove from heat and let cool slightly.
In a mixing bowl, combine the cream cheese, sour cream, and mayonnaise until creamy.
Stir in the garlic powder, salt, and pepper.
Fold in the caramelized onions and half of the grated Gruyere cheese.
Transfer the mixture to an oven-safe baking dish and sprinkle the remaining cheese on top.
Preheat the oven to 350°F (175°C). Bake for 25-30 minutes or until the dip is hot and bubbly, and the cheese is golden brown.
Remove from oven and let it cool for a few minutes before serving.
Notes
Serve warm with toasted baguette slices, pita chips, or fresh vegetable crudités. Garnish with fresh chives for an added pop of color.
Keyword caramelized onions, cheese dip, party appetizer